On a wavelength division multiplexing (WDM) optical network, a node at which multiple different ring networks intersect needs to receive a large quantity of WDM optical signals from different lines, and route these WDM optical signals to different lines according to destination nodes of these WDM optical signals. In addition, the node further has add and drop (Add/Drop) lines that are connected to an aggregation layer. The add line is used to switch optical signals that aggregate at the node from a low layer and that need to be sent to different lines to destination lines. The drop line is used to switch an optical signal that is from another node and whose destination node is the node to the node. Switching of the optical signals may be implemented by using an optical switch.
As optical network traffic is ever-increasing, there is an increasingly high requirement for throughputs of switching nodes on a backbone network and a metropolitan area network of an optical network. A three dimension micro-electro-mechanical system (3D-MEMS) optical switch is an important solution for meeting the continuously increasing throughput requirement. For example, FIG. 1a and FIG. 1b respectively show a prior-art typical switching node 100 and an N×N full cross-connect 3D-MEMS optical switch 120 in the switching node. As shown in FIG. 1a, the switching node 100 includes n wavelength division demultiplexers 110, the MEMS optical switch 120, and n wavelength division multiplexers 130. The switching node 100 can implement switching of N×N optical signals. Specifically, after optical signals from n nodes or lines are input to the n wavelength division demultiplexers 110, each optical signal is demultiplexed into m optical signals and the m optical signals are input to the MEMS optical switch 120. Optical signals that need to be dropped to a location in which the switching node is located are output from k drop ports to the location in which the switching node is located. (N−k) optical signals that need to be sent to other nodes are switched to destination output ports corresponding to destination nodes of the optical signals. In addition, optical signals that are from the location in which the switching node is located and that need to be switched to other nodes may be input from k add ports, and are switched to destination output ports corresponding to destination nodes of the optical signals, where N=n×m+k. Optical signals output from output ports of the MEMS optical switch 120 are input to the n wavelength division multiplexers 130, and each wavelength division multiplexer 130 combines input multiple optical signals into one optical signal for output. As shown in FIG. 1b, the MEMS optical switch 120 includes an input port array 121, an input MEMS mirror array 123, an output MEMS mirror array 125, and an output port array 127. The input poll array 121 and the input MEMS mirror array 123 may respectively include N input ports and N input MEMS mirrors, where N>1. The N input MEMS mirrors are corresponding to the N input ports on a one-to-one basis. The output MEMS mirror array 125 and the output port array 127 may respectively include N output MEMS mirrors and N output ports. The N output MEMS mirrors are corresponding to the N output ports on a one-to-one basis. In addition, each of the N input MEMS mirrors and the N output MEMS mirrors can perform two-dimensional deflection. As shown in FIG. 1b, an optical signal may enter the MEMS optical switch 120 from an input port. The optical signal may be an optical signal transmitted by another node or an optical signal added from the location in which the switching node is located. The optical signal may be transmitted to an input MEMS mirror corresponding to the input port. The input MEMS mirror may deflect by a specific angle, so that the optical signal is reflected to an output MEMS mirror in the output MEMS mirror array. The output MEMS mirror is corresponding to a destination output port of the optical signal. The output MEMS mirror may deflect by a specific angle, so that the optical signal is reflected to the destination output port corresponding to the output MEMS mirror. Finally, the optical switch 120 outputs the optical signal from the destination output port. An optical signal output from the destination output port may be transmitted to the node at which the MEMS optical switch 120 is located or transmitted to another node.
In FIG. 1b, it is assumed that each input MEMS mirror in the input MEMS mirror array 123 is in a rest state (at rest), that is, parallel with an xy plane, and an incidence angle for inputting a light beam is α. To enable a light beam reflected by an input MEMS mirror to reach any output MEMS mirror in the output MEMS mirror array, a light beam reflected by an input MEMS mirror located on the leftmost side needs to rotate clockwise by θ1 degrees, and correspondingly, the input MEMS mirror located on the leftmost side needs to rotate clockwise around a y axis by at least θ1/2 degrees. In this case, only a clockwise rotation capability of the input MEMS mirror located on the leftmost side is used. Similarly, an input MEMS mirror located on the rightmost side needs to rotate counterclockwise around the y axis by at least θ2/2 degrees. In this case, only a counterclockwise rotation capability of the input MEMS mirror located on the rightmost side is used. Because the input MEMS mirror array and the output MEMS mirror array include a same quantity of MEMS mirrors, all MEMS mirrors in the input MEMS mirror array and the output MEMS mirror array are the same, and a maximum clockwise rotation angle by which all the MEMS mirrors rotate around the y axis is the same as a maximum counterclockwise rotation angle by which all the MEMS mirrors rotate around the y axis. Consequently, θ1 and θ2 need to be less than the maximum rotation angle of the MEMS mirrors, which limits the quantity of MEMS mirrors in the input MEMS mirror array 123 and the output MEMS mirror array 125. Therefore, if a scale of integration of a MEMS optical switch needs to be increased, the maximum rotation angle of the MEMS mirrors needs to be increased, which is difficult to implement. In conclusion, it is difficult to implement a MEMS optical switch with larger-scale integration in the prior art, and it is difficult to meet a requirement for throughputs of switching nodes on a backbone network and a metropolitan area network.